Car Crashes and Road Traffic Accidents: The Causes

Since 2005 official accident records have included information on contributory factors. These insights have recently been correlated and have provided significant insights into the causes of road accidents on UK roads. Here we summarise the key findings.

A total of 77 categories of contributory factors, grouped together under 9 headings have been established. The headings are:

Driver/rider error or reaction

Injudicious action

Behaviour or experience

Road environment

Pedestrian only

Impairment or distraction

Vision affected

Special codes

Vehicle defects

By far the biggest cause of road accidents is driver/rider error or reaction, which causes 68% of all crashes.

The top ten most common causes of traffic accidents are:

Failed to look properly 35%

Failed to judge other persons's path or speed 18.9%

Careless, reckless or in a hurry 16.2%

Loss of control 14.7%

Poor turn or manoeuvre 14.1%

Travelling too fast for the conditions 10.2%

Slippery road due to weather 10.1%

Pedestrian failed to look properly 7.2%

Sudden braking 7.2%

Following too close 6.7%

Contributory Factor Reported in Accident

Fatal

Serious

Slight

All Accidents

Driver / Rider Error or Reaction

65.3%

61.8%

68.6%

67.5%

Failed to look properly

20.5%

29.3%

36.3%

35%

Failed to judge other persons's path or speed

11.6%

14%

20%

18.9%

Loss of control

34%

19.7%

13.4%

14.7%

Poor turn or manoeuvre

12%

13.8%

14.1%

14.1%

Sudden braking

3%

4.5%

7.7%

7.2%

Swerved

6.2%

4.2%

3.7%

3.8%

Junction overshoot

1.7%

1.9%

2.5%

2.3%

Failed to signal or misleading signal

0.6%

1.3%

2%

1.9%

Junction restart (moving off at a junction)

0.9%

1.1%

1.8%

1.7%

Passing too close to a cyclists, horse rider or pedestrian

1.1%

1.4%

1.4%

1.4%

Injudicious Action

31.4%

25%

26.1%

26%

Travelling too fast for conditions

15.9%

11.3%

9.9%

10.2%

Following too close

1.3%

2.8%

7.5%

6.7%

Exceeding speed limit

13.9%

7.2%

4.6%

5.2%

Disobeyed 'give way' or 'stop' sign markings

2.1%

2.8%

3.5%

3.4%

Disobeyed automatic traffic signal

1.0%

1.4%

1.8%

1.8%

Cyclist entered road from pavement

0.5%

1%

0.9%

0.9%

Illegal turn or direction of travel

0.7%

0.8%

0.7%

0.8%

Disobeyed pedestrian crossing facility

0.4%

0.7%

0.4%

0.4%

Vehicle travelling along pavement

0.4%

0.3%

0.3%

0.3%

Disobeyed double white lines

0.9%

0.5%

0.2%

0.2%

Behavior or Inexperience

28%

25.8%

24.4%

24.7%

Careless, reckless or in a hurry

17.2%

16.8%

16.1%

16.2%

Learner or inexperienced driver/rider

5.3%

5.5%

5.2%

5.3%

Aggressive driving

8.3%

5.1%

3.6%

3.9%

Nervous, uncertain or panic

1.1%

1.3%

1.8%

1.7%

Unfamiliar with model of vehicle

1.4%

1.1%

0.8%

0.8%

Inexperience of driving on left

0.4%

0.4%

0.5%

0.5%

Driving too slow for conditions or slow vehicle e.g. tractor

0.1%

0.1%

0.1%

0.1%

Road Environment

10.9%

13.3%

15.6%

15.1%

Slippery road (due to weather)

5.9%

7.9%

10.6%

10.1%

Road layout e.g. hill, bend, narrow carriageway

3.2%

2.8%

2.7%

2.7%

Deposit on road e.g. oil, mud

0.8%

1.7%

1.5%

1.5%

Animal or object in carriageway

0.8%

1.0%

1.2%

1.2%

Poor or defective road surface

0.7%

0.8%

0.6%

0.5%

Inadequate or masked roads signs or markings

0.4%

0.4%

0.5%

0.3%

Temporary road layout e.g. contraflow

0.2%

0.2%

0.3%

0.2%

Defective traffic signals

0.0%

0.1%

0.2%

0.1%

Traffic calming e.g. road humps

0.1%

0.2%

0.1%

0.1%

Pedestrian Only (casualty or uninjured)

18.2%

20.4%

11.5%

13.0%

Pedestrian failed to look properly

10.5%

14.8%

8.5%

9.5%

Pedestrian careless, reckless or in a hurry

3.4%

6.3%

3.6%

4%

Pedestrian crossing road masked by stationary or parked vehicle

1.9%

4.4%

2.4%

2.7%

Pedestrian failed to judge vehicle's path or speed

5.2%

4.5%

2.4%

2.8%

Pedestrian impaired by alcohol

4.1%

3.5%

1.5%

1.9%

Dangerous action in carriageway e.g. playing

2.2%

1.9%

0.9%

1.1%

Pedestrian wrong use of pedestrian crossing

1.2%

1.4%

0.7%

0.8%

Pedestrian wearing dark clothing at night

3.3%

1.3%

0.5%

0.7%

Pedestrian disability or illness, mental or physical

1.9%

0.8%

0.3%

0.4%

Pedestrian impaired by drugs (illicit or medicinal)

0.4%

0.3%

0.1%

0.2%

Impairment or Distraction

19.6%

14.2%

11.1%

11.7%

Impaired by alcohol

9.6%

7.4%

4.7%

5.2%

Distraction in vehicle

2.6%

1.7%

2.1%

2.1%

Fatigue

3.1%

1.8%

1.3%

1.4%

Distraction outside vehicle

1.0%

1.0%

1.5%

1.4%

Illness or disability, mental of physical

3.6%

1.8%

1.2%

1.3%

Impaired by drugs (illicit or medicinal)

2.2%

0.9%

0.4%

0.5%

Not displaying lights at night or in poor visibility

0.4%

0.4%

0.3%

0.3%

Cyclist wearing dark clothing at night

0.4%

0.4%

0.3%

0.3%

Driver using mobile phone

0.8%

0.3%

0.2%

0.2%

Uncorrected, defective eyesight

0.4%

0.2%

0.1%

0.2%

Vision Affected By

7.5%

9.2%

10.5%

10.3%

Stationary or parked vehicle(s)

1.1%

2.9%

3.2%

3.1%

Dazzling sun

1.5%

1.8%

2.2%

2.2%

Snow, sleet, snow or fog

1.5%

1.5%

1.9%

1.9%

Road layout e.g. bend, crest of hill

1.7%

1.5%

1.5%

1.5%

Vehicle blind spot

1.0%

1.0%

1.4%

1.2%

Vegetation

0.4%

0.4%

0.4%

0.4%

Dazzling headlights

1.4%

0.3%

0.3%

0.3%

Buildings, road signs, street furniture

0.2%

0.2%

0.2%

0.2%

Spray from other vehicles

0.1%

0.2%

0.2%

0.2%

Visor or windscreen dirty or scratched

0.2%

0.1%

0.1%

0.1%

Special Code

6.1%

5.2%

4.5%

4.6%

Other

4.4%

3.3%

2.7%

2.8%

Stolen vehicle

1.1%

1.0%

0.7%

0.8%

Emergency vehicle on call

0.3%

0.4%

0.6%

0.5%

vehicle in course of crime

0.4%

0.4%

0.4%

0.4%

vehicle door opened or closed negligently

0.1%

0.4%

0.4%

0.4%

Vehicle Defects

2.8%

2.2%

1.9%

1.9%

Tyres illegal, defective or under inflated

1.5%

0.9%

0.7%

0.7%

Defective brakes

0.7%

0.6%

0.6%

0.6%

Overloaded or poorly loaded vehicle or trailer

0.4%

0.3%

0.2%

0.2%

Defective lights or indicators

0.2%

0.2%

0.2%

0.2%

Defective steering or suspension

0.2%

0.2%

0.2%

0.2%

What this tells us is that the human error is far more likely to be the cause of a car crash than the road environment or a defective vehicle. This is regardless of what type of road the accident happened on or at what time.

Although the factors which cause traffic accidents are fairly consistent over a range of factors e.g. the time of accident there are some notable exceptions.

Rural and Urban Roads.
Road environment factors are reported in a larger proportion of accidents in rural areas than urban areas.

Pedestrian factors are reported in a larger proportion of accidents in urban areas than rural areas.

Urban Roads

Rural Roads

Failed to look properly

40.9%

Failed to look properly

26.1%

Failed to judge other person's path or speed

19.1%

Loss of control

23.3%

Careless, reckless or in a hurry

17.3%

Failed to judge other person's path or speed

18.8%

Poor turn or manouevre

15.0%

Slippery road (due to weather)

15.8%

Pedestrian failed to look properly

14.1%

Careless, reckless or in a hurry

14.6%

Loss of control

9.0%

Travelling too fast for conditions

14.2%

Travelling too fast for conditions

7.6%

Poor turn or manouevre

12.7%

Following too close

6.3%

Sudden Braking

9.3%

Slippery road (due to weather)

6.3%

Following too close

7.2%

Pedestrian careless reckless or in a hurry

6.0%

Learner or inexperienced driver/rider

6.6%

Learner and Inexperienced Drivers
Such
drivers are more vulnerable on rural roads than urban ones (see highlighted figure above). Also they are more likely to crash due to 'error or reaction' factors than drivers between 30 and 70. Car drivers under 25 have 'exceeding the speed limit', 'travelling too fast for the conditions' and 'learner/inexperienced' recorded more frequently than drivers over the age of 25.

Behaviour and inexperience factors are almost three times higher for the under 20's than the average for all ages.

10 Most Reported Factors For Cars: Drivers Age

Age 25 or below

Failed to look properly

18.4

Loss of control

14.5

Driver/rider careless, reckless or in a hurry

12.0

Failed to judge other person's path or speed

11.3

Travelling too fast for the conditions

10.4

Slippery road (due to weather)

9.9

Learner or inexperienced driver/rider

9.2

Poor turn or manoeuvre

7.8

Exceeding speed limit

6.0

Sudden braking

5.1

Age 26-69

Failed to look properly

18.0

Failed to judge other person's path or speed

9.6

Poor turn or manoeuvre

6.6

Driver/rider careless, reckless or in a hurry

6.6

Loss of control

5.5

Slippery road (due to weather)

5.1

Travelling too fast for the conditions

4.0

Sudden braking

3.5

following too close

3.5

Impaired by alcohol

2.5

Age 70 and over

Failed to look properly

28.4

Failed to judge other person's path or speed

15.6

Poor turn or manoeuvre

10.6

Loss of control

8.5

Driver/rider careless, reckless or in a hurry

5.8

Illness or disability, mental of physical

5.2

Dazzling sun

3.2

Disobeying 'Give Way' or 'Stop' sign or markings

3.2

Slippery road (due to weather)

3.1

Nervous, uncertain or panic

2.9

Gender Differences
Comparisons between men and women car drivers show little difference in the contributory factors reported, but 'careless, reckless or in a hurry, 'travelling too fast for the conditions' and 'impaired by alcohol' are recorded more frequently for men than women, while 'learner or inexperienced' is recorded more frequently for women.